Anagrams string checker in Java

Carvia Tech | July 24, 2020 | 2 min read | 1,334 views | Java Coding Challenges


Anagram

Two strings are called anagrams if they contain same set of characters but in different order. For example,

  • peek and keep are anagrams

  • spar and rasp are anagrams

  • listen and silent are anagrams

Approach 1: sorting of characters

  1. Sort characters within string for both the inputs.

  2. if the two strings are same after sorting, they are anagram else not.

Let’s write Java code that takes this approach and checks if two given inputs are anagrams or not.

AnagramChecker.java
import java.util.Arrays;

public class AnagramChecker {

    public boolean isAnagram(String input1, String input2) {
        char[] sortedWord1 = input1.toCharArray();
        Arrays.sort(sortedWord1);

        char[] sortedWord2 = input2.toCharArray();
        Arrays.sort(sortedWord2);

        return Arrays.equals(sortedWord1, sortedWord2);
    }
}

Here is the unit test for above method.

JUnit testcase
import org.junit.Test;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.*;

public class AnagramCheckerTest {

    @Test
    public void isAnagram() {
        AnagramChecker checker = new AnagramChecker();

        assertThat(checker.isAnagram("peek", "keep"), equalTo(true));
        assertThat(checker.isAnagram("mary", "army"), equalTo(true));

        assertThat(checker.isAnagram("dart", "mart"), equalTo(false));
    }
}

Approach 2: Using count of characters for both words and compare

Alternatively, we can count the number of characters in both words and compare it for exactness. This approach is slightly efficient, as it has time complexity of Big O(n) compared to Big O(n log n) in earlier case.

AnagramEfficient.java
public class AnagramEfficient {

    public boolean isAnagram(String first, String second) {
        int[] letterCount = new int[126];

        for (char ch : first.toCharArray()) {
            letterCount[ch]++;
        }

        for (char ch : second.toCharArray()) {
            letterCount[ch]--;
        }

        for (int count : letterCount) {
            if (count != 0)
                return false;
        }
        return true;
    }
}

Here we are assuming that input is always an ASCII text without unicode support.

We can lowercase the input in both the approaches to make it case-insensitive.


Java Coding Challenges:
  1. Reverse position of words in a string using recursion
  2. Check if the given string is palindrome
  3. Find two numbers of which the product is maximum in an array
  4. Check a number is Prime: Java Coding Problem
  5. Create anagram buckets from a given input array of words
  6. Reverse a string using recursion in Java
  7. Java Program to find Factorial of a number
See all articles in Java Coding Challenges
Top articles in this category:
  1. Create anagram buckets from a given input array of words
  2. SDET Java Coding Challenges
  3. Check if the given string is palindrome
  4. 50 SDET Java Interview Questions & Answers
  5. Reverse a string using recursion in Java
  6. Palindrome checker in Java
  7. Rest Assured API Testing Interview Questions

Find more on this topic:

Recommended books for interview preparation: